The primary objective of this research is to study the effects of undernutrition of neonatal onset on growth and maturation of the spinal cord. The undernourished state is achieved by fostering rat pups born of a normally nourished dam to a dam maintained on a diet reduced in quantity by 25% or 50% of the amount consumed by non-restricted rats. The laboratory rat has been selected because of the immature status of its nervous system at birth and throughout the pre-weaning period. In addition, the neuroglial population which is the ultimate concern of these studies develops during this pre-weaning period. The pups suckled by the restricted dams will be compared with their littermates suckled by their natural or the foster non-restricted dams. Gross aspects of spinal cord development, such as spinal cord length and weight, are being studied as well as the neuroglial population and its proliferative capacities. The latter studies are carried out by light microscopic autoradiography.